This invention relates to motion picture film transport movements for cameras and projectors, and particularly high speed cameras employing large format 35 mm and 70 mm film. Film transport movements are characterized by crank operated claw pins and register pins that advance and position the film respectively, for rapid sequential exposure or projection of the picture frames. The crank motions are made with precision and are balanced to prevent vibration, there being rotating drive parts, reciprocating parts and oscillating parts, the reciprocating and oscillating parts being subject to motion reversals which can be detrimental. That is, mass inertia is to be considered and the accelerations and decelerations minimized.
Heretofore, the film transport claw pins have been integral with the transport arm that reciprocates radially from its oscillating axis, by separate crank and connecting rod means; one means for oscillation and one means for reciprocation. As a result of these combined reciprocating and oscillating motions there is an unwanted increase in the acceleration and deceleration of the claw pins at the points of entry into and exit from the film perforations, it being a general object of this invention to reduce said increases. With this invention the acceleration and deceleration are decreased approximately 25%.
Normal film speed is 24 frames per second at 1440 RPM. However, high speed cameras of the type under consideration operate up to 280 frames per second at 16,800 RPM. A moderate high speed camera operating, for example, at 233 frames per second driven at 14,000 RPM has parts with mass inertia accelerations and decelerations of approximately 4000 gravities, at the aforesaid points of entry and exit of the claw pins into and out of the film.
Therefore and in view of the foregoing, it is an object of this invention to combine the crank and connecting rod means in structural relation with the claw pin arm and claw pins to decrease substantially the accelerations and decelerations of the claw pins and a carrier provided therefor. With the present invention, the claw pin arm is restricted to oscillating motion, and the claw pin carrier reciprocates radially therefrom about the center of arm oscillation.
Accordingly, it is an object of this invention to advantageously employ pure oscillatory motion in the claw arm, for the purpose of reducing acceleration and deceleration forces, when combined with the crank and connecting rod means that drive the same. And, it is another object of this invention to advantageously carry the claw pins by a carrier that reciprocates separately from said oscillating motion when combined with the crank and connecting rod means that drive the same.
Since mass inertia is of prime concern in this high speed film transport, the weight of the oscillating and reciprocating parts is of particular concern. Therefore, it is an object of this invention to reduce the weight of all such parts, namely the connecting rods, wrist pins, pivot block and claw pin arm, claw pin carrier and shaft, and the claw pins. Additionally, the oscillating and reciprocating parts of the register pin motion are of reduced weight, namely the connecting rods, wrist pins, drive bracket and the register pins. In practice, these parts and elements are made of Beryllium or the like, a metallic element of extreme strength and lightness.
The foregoing and various other objects and features of this invention will be apparent and fully understood from the following detailed description of the typical preferred form and application thereof, throughout which description reference is made to the accompanying drawings.